The present invention relates to a hole threading tap or a "chasing tap" and in particular relates to a chasing tap with replaceable thread cutting heads or "chasers".
It is known to provide a die head for a quick change chaser, such as disclosed in U.S. Pat. No. 2,864,102. In this patent, a longitudinal cylindrical die body is provided with longitudinally extending recesses around its outer periphery in which individual chasers are clamped. A removable sleeve is provided which, by camming action, locks the chasers into the die body recesses for performing a cutting operation.
U.S. Pat. No. 3,812,547 describes a tool holder with interchangeable inserts for a tangent chaser. Interchangeable threading dies for an automatic self-opening tangent threading die head permit a range of thread pitches and diameters to be cut with a single die head.
U.S. Pat. No. 4,531,863 relates to a thread-cutting apparatus which includes an indexable insert having multiple thread-cutting profiles.
U.S. Pat. No. 5,112,162 describes a thread-milling cutter assembly. The assembly includes a cutting tool comprised of tool hardened steel having a holder end and an opposite end. A series of axially extending slots are provided on the tool on an outer circumference of the opposite end. A series of cutter bits are mounted in the slots and bottomed on the jig ground pins positioned at the radially inner end of the associated slot. A wedge-shaped shim is used to hold the replaceable cutter bit in place.
One of the drawbacks of the aforementioned prior art is that the head portions or tool holding portions of the chaser assemblies do not provide the flexibility of using universal or standard threading chasers or head portions for a variety of bore diameters.